Abstract: An apparatus and method for preparing an inside diagonal corner insert to a laminated plastic countertop surface. The diagonal corner insert transects the inside corner of the countertop and permits the countertop to accommodate a rotatable shelf apparatus thereunder. Dimensionally corresponding female and male templates are provided so that a cutting tool guided by the templates will produce a corresponding male insert for the void created in the countertop with the female template. The countertop and template are advantageously secured in an easily accessible position by a jig apparatus which utilizes pneumatic pistons for securing both the workpiece and the templates.